Assembly type nozzle diaphragm, and method of assembling the same

ABSTRACT

An assembled nozzle diaphragm according to the present invention includes a diaphragm outer ring  15  having a groove  23  opened toward an inner diameter side to be continuous in an inner peripheral direction of the diaphragm outer ring  15 ; a diaphragm inner ring  16  having a groove  28  opened toward an outer diameter side to be continuous in an outer peripheral direction of the diaphragm inner ring  16 ; and a nozzle blade  14  having a diaphragm outer ring insertion portion  12  on one end and a diaphragm inner ring insertion portion  13  on the other end, in which the groove  23  opened toward the inner diameter side of the diaphragm outer ring  15  and the diaphragm outer ring insertion portion  12  of the nozzle blade  14  are shaped to be fitted to each other only in a circumferential direction of each of the groove  23  and the diaphragm outer ring insertion portion  12 , and in which the groove  28  opened toward the outer diameter side of the diaphragm inner ring  16  and the diaphragm inner ring insertion portion  13  of the nozzle blade  14  are shaped to be fitted to each other only in one of circumferential direction and diameter direction of each of the groove  28  and the diaphragm inner ring insertion portion  16 . According to this structure, the assembled nozzle diaphragm and an its assembling method can be provided so as to be capable of modifying and simplifying a structure of a turbine nozzle and facilitating assembling working without performing welding operation.

TECHNICAL FIELD

[0001] The present invention relates to an assembled nozzle diaphragmapplied to a steam turbine and a method of assembling the nozzlediaphragm.

BACKGROUND ART

[0002] Generally, there has been often provided so-called an axial flowsteam turbine, having large capacity, including a plurality of sages,arranged along steam flow direction, each comprising in combination aturbine nozzle (turbine stationary (stator) blade) and a turbine movingor movable (rotor) blade.

[0003] The axial flow steam turbines will be roughly classified intoreaction type and impulse type.

[0004] The steam turbine of the impulse type causes thermal energy of asteam to perform more expansion work using each turbine nozzle,transforms the steam after the expansion work to a deflected flow usingeach turbine moving blade, and guides the resultant deflected flow tothe next stage.

[0005] In the turbine nozzle that converts most of the thermal energy ofthe steam to kinetic energy, a large pressure difference occurs betweena steam inlet and a steam outlet of the turbine nozzle. To deal withthis pressure difference, therefore, the turbine nozzle adopts adiaphragm structure as shown in FIG. 24.

[0006] The turbine nozzle of the diaphragm structure shown in FIG. 24 isconstituted as follows. A ring body 1 is divided into two portions on ahorizontal joint surface 2, both ends of nozzle blades (nozzle plates) 3arranged in ring columns are supported by a diaphragm outer ring 4 and adiaphragm inner ring 5, and a labyrinth packing mounting groove 6 isprovided in an inner periphery of the diaphragm inner ring 5 that facesa turbine shaft (not shown).

[0007] Further, the turbine nozzle is so-called a weld-type turbinenozzle in which at a time when the nozzle blade 3 is connected to thediaphragm outer ring 4 and the diaphragm inner ring 5, the nozzle blade3 is fixedly attached thereto by welding portions 8 a and 8 b throughwear plates 7 a and 7 b, respectively, as shown in FIG. 25.

[0008] On the other hand, in so-called a counter-flow (double flow)turbine that divides the steam flow to a left flow and a right flow atits inlet as shown in FIG. 30, at a time when top sides of a firstdivided-flow nozzle blade 49 and a second divided-flow nozzle blade 50are supported by a first divided-flow diaphragm outer ring 52 and asecond divided-flow diaphragm outer ring 53, respectively, the first andsecond divided-flow nozzle blades 49 and 50 are fixedly attached to thefirst and second divided-flow diaphragm outer rings 52 and 53 by weldingportions 54 a and 54 b and bottoms of the first and second divided-flownozzle blades 49 and 50 are fixed by welding portions 54 c and 54 dusing a shared diaphragm inner ring 51 shared between the first andsecond divided-flow nozzle blades 49 and 50, respectively.

[0009] The weld-type turbine nozzles as shown in FIG. 25 have beenemployed long and have given actual results. However, as internationalcompetition has been increasingly harsh, the market has demanded marestrictly improved performances and cost reduction for turbine nozzles.In light of such demand, the following matters, which have not beenregarded seriously, constitute important matters or problems to beconsidered or solved.

[0010] (1) As to performance: deterioration of performance caused bymanufacturing error resulting from welding distortion in the case of theweld-type turbine nozzle.

[0011] The most serious effect of the welding distortion is thedeviation of inside and outside diameters of a steam path from designeddiameters, respectively. For example, as shown in FIG. 26, even if theturbine nozzle is designed into so-called a lap (step)-free state inwhich both a blade root portion (blade base portion) 10 and a blade tipportion (top portion) 11 are formed linearly, both the blade rootportion 10 and blade tip portion 11 actually have positive (+) ornegative (−) laps relative to the designed values as their respectivereference positions as shown in FIG. 27 by the effect of the weldingdistortion.

[0012] A turbine stage efficiency has been confirmed by an experimentbased on the positive or negative laps, it has been found that as thepositive or negative laps are greater, the deterioration of the turbinestage efficiency is higher. For this reason, even if a method forminimizing the welding distortion is discovered by trial and error, thismethod naturally has its limit, and as a result of the long-time use ofthe turbine nozzle, great positive or negative laps often appear again.

[0013] Furthermore, a concept of so-called offset design, in which adesigned position of the non-dimensional lap is set at a positiveposition indicated by an arrow AR at the time of design on theassumption that a negative lap occurs, has been introduced so as to tryto maintain the turbine stage efficiency at the maximum value (Mmax)during the operation of the turbine nozzle. However, this methodnaturally has its limit, as well.

[0014] (2) As to cost: since there are many welding steps, it isdifficult to realize cost reduction.

[0015]FIG. 29 illustrates one example in which manufacturing costcomposition ratios of the weld-type turbine nozzle in the form of acircular graph. In the example of FIG. 29, a welding cost reaches about38 percents of a total manufacturing cost. As a result, even if it isattempted to effectively reduce a material cost and a working cost,there is a limit to the cost reduction. In addition, since it isdifficult to mechanize and automate welding operation 100 percents, itis difficult to reduce the welding cost itself, accordingly.

[0016] The present invention has been achieved under thesecircumstances. It is an object of the present invention to modify andthereby simplify a turbine nozzle structure and to provide a assemblednozzle diaphragm which can be easily assembled without performing awelding operation and a method of assembling such nozzle diaphragm.

DISCLOSURE OF THE INVENTION

[0017] An assembled nozzle diaphragm according to the present invention,to achieve the above-mentioned object, comprises: a diaphragm outer ringhaving a groove opened toward an inner diameter side to be continuous inan inner peripheral direction of the diaphragm outer ring; a diaphragminner ring having a groove opened toward an outer diameter side to becontinuous in an outer peripheral direction of the diaphragm inner ring;and a nozzle blade having an insertion portion for the diaphragm outerring provided on one end and having an insertion portion for thediaphragm inner ring provided on the other end, wherein the grooveopened toward the inner diameter side of the diaphragm outer ring andthe diaphragm outer ring insertion portion of the nozzle blade areshaped to be fitted into each other only in a circumferential directionof each of the groove and the diaphragm outer ring insertion portion,and the groove opened toward the outer diameter side of the diaphragminner ring and the diaphragm inner ring insertion portion of the nozzleblade are shaped to be fitted into each other only in one ofcircumferential direction and diameter direction of each of the grooveand the diaphragm inner ring insertion portion.

[0018] In a preferred embodiment of the above aspect of the presentinvention, an upstream side surface of the diaphragm outer ringinsertion portion, which is directed toward a flow of a fluid (steam),is formed in combination of a protruded hook portion and a stepped blockportion provided to be continuous to the protruded hook portion, and theprotruded hook portion and the stepped block portion extend in thecircumferential direction.

[0019] In addition, the diaphragm inner ring insertion portion may havea convex columnar piece formed at an intermediate position, and theconvex columnar piece may extend in the circumferential direction.

[0020] The diaphragm outer ring has a cap groove formed in thecircumferential direction, the cap groove including a protruded hookportion at an inlet.

[0021] Further, the diaphragm inner ring may have a concave grooveformed in the circumferential direction.

[0022] A fitting gap between the diaphragm outer ring insertion portionand the diaphragm outer ring is set in a range of 0.03 to 0.12millimeters.

[0023] The fitting gap set in the range of 03 to 0.12 millimetersbetween the diaphragm outer ring insertion portion and the diaphragmouter ring is at least one of a gap between a surface on a head side ofthe diaphragm outer ring insertion portion parallel to a flow of a fluidand the diaphragm outer ring and a gap between a surface on an upstreamside surface of the diaphragm outer ring insertion portion in thediameter direction and the diaphragm outer ring.

[0024] A fitting gap between the diaphragm inner ring insertion portionand the diaphragm inner ring is set in a range of 0.03 to 0.12millimeters.

[0025] The fitting gap set in the range of 03 to 0.12 millimetersbetween the diaphragm inner ring insertion portion and the diaphragminner ring is a gap between a surface of a columnar piece of thediaphragm inner ring insertion portion in the diameter direction and thediaphragm inner ring.

[0026] Moreover, the diaphragm outer ring insertion portion may beformed in combination of protruded hook portions provided on an upstreamside surface directed toward a flow of a fluid and a downstream sidesurface along the flow of the fluid, respectively, stepped blockportions provided to be continuous to the respective protruded hookportions, and protruded base portions provided to be continuous to therespective stepped block portions.

[0027] The diaphragm outer ring insertion portion is constituted incombination of a columnar piece directed toward the diameter directionand a protruded base portion provided to be continuous to the columnarpiece.

[0028] An upstream side surface of the diaphragm outer ring insertionportion which surface is directed toward a flow of a fluid can be formedin combination of a protruded hook portion, a stepped block portionprovided to be continuous to the hook portion, and a protruded baseportion provided to be continuous to the block portion, a ring piece isattached to the block portion, and fixing means is provided on thediaphragm outer ring so as to apply a pressing force to the diaphragmouter ring insertion portion.

[0029] An upstream surface of the diaphragm outer ring insertion portionwhich is directed toward a flow of a fluid may be formed in combinationof a protruded hook portion, a stepped block portion provided to becontinuous to the hook portion, and a protruded base portion provided tobe continuous to the block portion, and a shakiness prevention piece maybe provided on a fitting surface on which the diaphragm outer ringinsertion portion is fitted to the diaphragm outer ring.

[0030] This shakiness prevention piece is provided at least one of a gapbetween a surface on a head side of the diaphragm outer ring insertionportion parallel to the flow of the fluid and the diaphragm outer ringand a gap between a surface of the upstream side surface of thediaphragm outer ring insertion portion in the diameter direction and thediaphragm outer ring.

[0031] This shakiness prevention piece may be provided at a cornerportion of the upstream side surface on a head side of the diaphragmouter ring insertion portion.

[0032] In addition, a plurality of the nozzle blades each supported bythe diaphragm outer ring and the diaphragm inner ring may be arranged atcounterflow positions along a flow of a fluid to be divided, and theplurality of nozzle blades arranged at the counterflow positions may besupported by the single diaphragm inner ring.

[0033] On the other hand, a plurality of the nozzle blades eachsupported by the diaphragm outer ring and the diaphragm inner ring maybe arranged at counterflow positions along a flow of a fluid to bedivided, and the diaphragm outer ring insertion portion of each of theplurality of nozzle blades arranged at the counterflow positions may besupported by the single diaphragm outer ring.

[0034] Furthermore, in another aspect of the present invention, theabove-mentioned object can be also achieved by providing an assemblednozzle diaphragm comprising: a diaphragm outer ring having a grooveopened toward an inner diameter side to be continuous in an innerperipheral direction of the diaphragm outer ring; a diaphragm inner ringhaving a groove opened toward an outer diameter side to be continuous inan outer peripheral direction of the diaphragm inner ring; and a nozzleblade having an insertion portion for the diaphragm outer ring providedon one end and having an insertion portion for the diaphragm inner ringprovided on the other end, wherein the diaphragm inner ring includes anozzle blade inner periphery-side member formed integrally with thenozzle blade.

[0035] This diaphragm outer ring may include a shakiness preventionpiece on a fitting surface on which the diaphragm outer ring insertionportion is fitted to the diaphragm outer ring.

[0036] Moreover, the above-mentioned object can be also achieved byproviding an assembled nozzle diaphragm comprising: a diaphragm outerring having a groove opened toward an inner diameter side to becontinuous in an inner peripheral direction of the diaphragm outer ring;and a nozzle blade having an insertion portion for the diaphragm outerring provided on one end and a diaphragm inner ring provided on theother end, wherein a plate is inserted into the diaphragm inner ring.

[0037] Still furthermore, the above-mentioned object can be achieved byproviding, in a further aspect, a method of assembling a nozzlediaphragm which comprises a diaphragm outer ring having a groove openedtoward an inner diameter side to be continuous in an inner peripheraldirection of the diaphragm outer ring, a diaphragm inner ring having agroove opened toward an outer diameter side to be continuous in an outerperipheral direction of the diaphragm inner ring, and a nozzle bladehaving an insertion portion for the diaphragm outer ring provided on oneend and an insertion portion for the diaphragm inner ring provided onthe other end, the method characterized by comprising the steps of:working the diaphragm outer ring to be divided in half to a diaphragmouter ring upper half portion and a diaphragm outer ring lower halfportion at a horizontal joint surface position substantially at 180degrees so as to constitute the diaphragm outer ring of a ring body;working the diaphragm inner ring to be divided in half to a diaphragminner ring upper half portion and a diaphragm inner ring lower halfportion at a horizontal joint surface position substantially at 180degrees so as to constitute the diaphragm inner ring of the ring body;fitting the diaphragm outer ring insertion portion of the nozzle bladefrom a horizontal joint surface of one of the diaphragm outer ring upperhalf portion and the diaphragm outer ring lower half portion toward ahorizontal joint surface of the other one of the diaphragm outer ringupper half portion and the diaphragm outer ring lower half portion so asto sequentially insert, one by one, the nozzle blades of a preset numberin a circumferential direction; fixing the plurality of inserted nozzleblades by stopper pieces on the horizontal joint surfaces of the onehalf portion and on the horizontal joint surface of the other halfportion, respectively; inserting the diaphragm inner ring upper halfportion and the diaphragm inner ring lower half portion into the innerring insertion portion of the nozzle blade from an inside diameterdirection of the inner ring insertion portion; fixing the plurality ofinserted nozzle blades by stopper pieces on the horizontal joint surfaceof the inserted diaphragm inner ring upper half portion and thehorizontal joint surface of the inserted diaphragm inner ring lower halfportion, respectively; and fixing the diaphragm inner ring upper halfportion and the diaphragm outer ring upper half portion integrated withthe nozzle blades of the preset number to the diaphragm inner ring lowerhalf portion and the diaphragm outer ring lower half portion integratedwith the nozzle blades of the preset number on the respective horizontaljoint surfaces.

[0038] In this nozzle diaphragm assembling method, a fitting gap betweenthe diaphragm outer ring insertion portion and the diaphragm outer ringis set in a range of 0.03 to 0.12 millimeters.

[0039] In addition, the fitting gap set in the range of 0.03 to 0.12millimeters between the diaphragm outer ring insertion portion and thediaphragm outer ring is at least one of a gap between a surface on ahead side of the diaphragm outer ring insertion portion parallel to aflow of a fluid and the diaphragm outer ring and a gap between a surfaceon an upstream side surface of the diaphragm outer ring insertionportion in the diameter direction and the diaphragm outer ring.

[0040] Further, a fitting gap between the diaphragm inner ring insertionportion and the diaphragm inner ring is set in a range of 0.03 to 0.12millimeters.

[0041] The fitting gap set in the range of 0.03 to 0.12 millimetersbetween the diaphragm inner ring insertion portion and the diaphragminner ring exists in the diameter direction of a columnar piece of thediaphragm inner ring insertion portion.

[0042] The assembled nozzle diaphragm according to the present inventionhaving the characteristic features mentioned above can utilize thesimple assembly structure in which the diaphragm outer ring insertionportion provided on one end of the nozzle blade is fitted to thediaphragm outer ring and in which the diaphragm inner ring insertionportion provided on the other end of the nozzle blade is fitted to thediaphragm inner ring. Therefore, at the time when the assembled nozzlediaphragm according to the present invention is applied to, for example,the steam turbine, the path width of the steam path can be kept exactlyat the designed dimension and the turbine nozzle can be operated withfar higher turbine stage efficiency.

[0043] In addition, with the nozzle diaphragm assembling methodaccording to the present invention, the nozzle blade can be freely movedrelative to the diaphragm inner and outer rings. Therefore, even if adamage such as a crack occurs to the nozzle blade during the operationof the steam turbine, it suffices to exchange only the nozzle blade towhich the damage or the like occurs. Thus, differently from theconventional art, it is unnecessary to exchange the entire diaphragm andit is therefore possible to further reduce exchange operation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044]FIG. 1 is a sectional view which illustrates a first embodiment ofan assembled nozzle diaphragm according to the present invention.

[0045]FIG. 2 illustrates a nozzle blade pulled out from a diaphragmouter ring and a diaphragm inner ring shown in FIG. 1.

[0046]FIG. 3 is a perspective view of the nozzle blade shown in FIG. 2from an inclined direction of a front edge of the nozzle blade.

[0047]FIG. 4 illustrates the diaphragm outer ring pulled out from thenozzle blade shown in FIG. 1.

[0048]FIG. 5 is a cross-sectional view taken along a line V-V shown inFIG. 4.

[0049]FIG. 6 illustrates the diaphragm inner ring pulled out from thenozzle blade shown in FIG. 1.

[0050]FIG. 7 is a cross-sectional view taken along a line VII-VII shownin FIG. 6.

[0051]FIG. 8 is a perspective view illustrating a state that a pluralityof nozzle blades are bound together.

[0052]FIG. 9 illustrates a horizontal joint surface of the diaphragmouter ring and that of the diaphragm inner ring.

[0053]FIG. 10 illustrates a modified example of the horizontal jointsurface of the diaphragm outer ring and that of the diaphragm innerring.

[0054]FIG. 11 is a sectional view illustrating a second embodiment ofthe assembled nozzle diaphragm according to the present invention.

[0055]FIG. 12 is a sectional view illustrating a third embodiment of theassembled nozzle diaphragm according to the present invention.

[0056]FIG. 13 is a sectional view illustrating a fourth embodiment ofthe assembled nozzle diaphragm according to the present invention.

[0057]FIG. 14 is a sectional view illustrating a fifth embodiment of theassembled nozzle diaphragm according to the present invention.

[0058]FIG. 15 is a sectional view illustrating a sixth embodiment of theassembled nozzle diaphragm according to the present invention.

[0059]FIG. 16 is a sectional view illustrating a seventh embodiment ofthe assembled nozzle diaphragm according to the present invention.

[0060]FIG. 17 is a sectional view illustrating an eighth embodiment ofthe assembled nozzle diaphragm according to the present invention.

[0061]FIG. 18 is a sectional view illustrating a ninth embodiment of theassembled nozzle diaphragm according to the present invention.

[0062]FIG. 19 is a sectional view illustrating a tenth embodiment of theassembled nozzle diaphragm according to the present invention.

[0063]FIG. 20 is a sectional view illustrating an eleventh embodiment ofthe assembled nozzle diaphragm according to the present invention.

[0064]FIG. 21 is a flow chart which illustrates the steps of assemblingprocedures of the assembled nozzle diaphragm according to the first tosecond embodiments of the present invention.

[0065]FIG. 22 is a flow chart which illustrates the steps of assemblingprocedures of the assembled nozzle diaphragm according to the fourthembodiment of the present invention.

[0066]FIG. 23 is a flow chart which illustrates the steps of assemblingprocedures of the assembled nozzle diaphragm according to the fifth toseventh embodiments of the present invention.

[0067]FIG. 24 is a perspective view illustrating a conventional nozzlediaphragm divided in half.

[0068]FIG. 25 illustrates a conventional nozzle diaphragm of a weldtype.

[0069]FIG. 26 is an illustration used to explain a designed path widthof a steam path.

[0070]FIG. 27 is an illustration used to explain an actual path width ofthe steam path.

[0071]FIG. 28 is a diagram which shows a fluctuation in turbine stageefficiency due to a fluctuation in a lap of the steam path width.

[0072]FIG. 29 is a circular graph which illustrates details of amanufacturing cost of the conventional turbine nozzle.

[0073]FIG. 30 illustrates a nozzle diaphragm of the conventional weldtype and a counter-flow (double flow) type.

[0074]FIG. 31 is a schematic longitudinal sectional view of an axialflow turbine provided with the assembled nozzle diaphragm.

BEST MODE FOR CARRYING OUT THE INVENTION

[0075] The embodiments of an assembled nozzle diaphragm and anassembling method thereof according to the present invention will bedescribed hereunder with reference to the accompanying drawings by wayof reference numerals added to the drawings. In the respectiveembodiments, the assembled nozzle diaphragm is applied to a steamturbine. Reference numeral ST in the drawings denotes a steam flow inthe steam turbine.

[0076]FIG. 31 illustrates stages of an axial flow steam turbine 100 thatprovided with the assembled nozzle diaphragm. Each nozzle blade 104 isattached to a diaphragm outer ring 102 attached to a turbine casing 101and a diaphragm inner ring 103 so as to form a nozzle blade flow path. Aplurality of turbine moving (rotor) blades 106 is arranged downstream ofthis nozzle blade flow path. The moving blades 106 are built up orassembled in columns at predetermined intervals on an outer periphery ofa rotor wheel 105 in a circumferential direction, and a cover 107 thatprevents leakage of a working fluid is attached to an outer peripheralend of each moving blade 106.

[0077] In FIG. 31, the fluid, that is, steam ST flows from a rightdirection (upstream side) of the steam turbine to a left direction(downstream side) thereof. Further, it is to be noted that, in therespective embodiments, at the time when the assembled nozzle diaphragmaccording to the present invention is applied to the steam turbine, theconstituent elements of the assembled nozzle diaphragm are provided atpositions shown in FIG. 31 even without so specified.

[0078]FIG. 1 is an elevational section which illustrates the firstembodiment of the assembled nozzle diaphragm according to the presentinvention.

[0079] The assembled nozzle diaphragm in this embodiment is constitutedso that a nozzle blade (nozzle plate) 14 that includes a diaphragm outerring insertion portion 12 and a diaphragm inner ring insertion portion13 on both ends, respectively, a diaphragm outer ring 15 to which thediaphragm outer ring insertion portion 12 is fitted and which supports ahead of the nozzle blade (nozzle plate) 14, and a diaphragm inner ring16 to which the diaphragm inner ring insertion portion 13 is fitted andwhich supports a bottom of the nozzle blade (nozzle plate) 14.

[0080] As shown in FIGS. 2 and 3, the diaphragm outer ring insertionportion 12 is formed together with the nozzle blade 14 by precisioncasting or by being integrally cut out from a nozzle blade elementassembly through a machining process. An upstream side surface portion19 of the nozzle outer ring insertion portion 12 directed toward a flowof the steam ST in a case where this assembled nozzle diaphragm isincorporated to the steam turbine is formed to be protruded as a whole.This upstream side surface portion 19 is formed as a ring block bodyincluding a hook portion 17 and a block portion 18 formed in a stepform, and the upstream side surface portion 19 extends in thecircumferential direction (a moving blade rotating direction on aperpendicular plane relative to the steam flow).

[0081] Further, the diaphragm inner ring insertion portion 13, similarlyto the diaphragm outer ring insertion portion 12 shown in FIGS. 2 and 3,is formed together with the nozzle blade 14 by precision forging or bybeing integrally cut out from the nozzle blade element assembly by themachining work. The diaphragm inner ring insertion portion 13 includes aconvex columnar piece 20 in an intermediate portion and this columnarpiece 20 is formed into a ring block body extending in thecircumferential direction.

[0082] As shown in FIG. 4, the diaphragm outer ring 15, to which thediaphragm outer ring insertion portion 12 is fitted, is formed as a ringbody and divided in half to an outer ring upper half portion 21 and anouter ring lower half portion 22 on a horizontal joint surface HJS1. Thediaphragm outer ring 15 divided in half includes a protruded hookportion 24 at an inlet of a cap or cap-shaped groove 23, and this hookportion 24 applies a pressing force to the stepped block portion 18 ofthe diaphragm outer ring insertion portion 12 and engages with andsupports the hook portion 17 of the diaphragm outer ring insertionportion 12.

[0083] Namely, the presence of the cap-shaped groove 23 and the hookportion 24 of the diaphragm outer ring 15 enables the diaphragm outerring insertion portion 12 of the nozzle blade 14 to be fitted andinserted into the diaphragm outer ring 15 only on the horizontal jointsurface HJS1 while the nozzle blade 14 cannot be inserted into thediaphragm outer ring 15 in the other regions.

[0084] When the diaphragm outer ring insertion portion 12 issuccessively fitted to the cap-shaped groove 23 formed in the diaphragmouter ring 15 and the diaphragm outer ring insertion portion 12 isarranged on an entire periphery of the diaphragm outer ring 15, theouter ring upper half portion 21 and the outer ring lower half portion22 of the diaphragm outer ring 15 are then fastened by means of bolts 25a and 25 b as shown in FIG. 4. The diaphragm outer ring 15 is engagedwith and supported by a casing (not shown).

[0085] As shown in FIG. 6, the diaphragm inner ring 16, to which thediaphragm inner ring insertion portion 13 is fitted, is formed as a ringbody and divided in half to an inner ring upper half portion 26 and aninner ring lower half portion 27 on a horizontal joint surface HJS2similarly to the diaphragm outer ring 15. As shown in FIG. 7, thediaphragm inner ring 16 divided in half includes a concave groove 28 ona head side (outer diameter side) and a labyrinth packing groove 29 on abottom side (inner diameter side). The diaphragm inner ring insertionportion 13 is fitted to the concave groove 28 on the head side, alabyrinth packing 30 is fitted into the labyrinth packing groove 29, andthen the inner ring upper half portion 26 and the inner ring lower halfportion 27 are joined together by a key (not shown) as shown in FIG. 6.

[0086] Namely, the assembled nozzle diaphragm has a structure in whichthe diaphragm inner ring insertion portion 13 of the nozzle blade 14 isfitted to the diaphragm inner ring 16 through the engagement of thesimple concave groove 28 and the simple convex columnar piece 20.Therefore, it is unnecessary to move the diaphragm inner ring 16 fromthe horizontal joint surface HJS2 in the circumferential direction so asto successively insert the diaphragm inner ring insertion portion 13 ofthe nozzle blade 14 into the diaphragm inner ring 16, and the diaphragminner ring insertion portion 13 can be simply inserted thereinto from aninside diameter direction (from a downward direction to an upwarddirection in FIG. 7).

[0087] In addition, after the diaphragm outer ring insertion portion 12and the diaphragm inner ring insertion portion 13 are fitted into thediaphragm outer ring 15 and the diaphragm inner ring 16, respectively,stopper pieces 31 a and 31 b are mounted to the diaphragm outer ring 15and the diaphragm outer ring insertion portion 12 and also to thediaphragm inner ring 16 and the diaphragm inner ring insertion portion16 on the horizontal joint surfaces HJS1 and HJS2, respectively, shownin FIG. 9, whereby the outer and inner ring upper half portions 21 and26 and the outer and inner ring lower half portions 22 and 27 of thediaphragm outer ring 15 and the diaphragm inner ring 16 both divided inhalf are fixedly attached to each other, respectively. The fixing of thediaphragm outer ring insertion portion 12 to the diaphragm outer ring 15and that of the diaphragm inner ring insertion portion 13 to thediaphragm inner ring 16 may be made by, for example, using fasteningmembers 32 a and 32 b, respectively, as shown in FIG. 10.

[0088] In this embodiment, the fitting of the diaphragm outer ringinsertion portion 12 into the diaphragm outer ring 15 and that of thediaphragm inner ring insertion portion 13 into the diaphragm inner ring16 are made for each nozzle blade 14. However, the present invention isnot limited to this embodiment. As shown in, for example, FIG. 8, it maybe possible to provide a nozzle diaphragm block body 33 that bindstogether a plurality of nozzle blades 14 such as three nozzle blades andallows the nozzle blades 14 to be supported by the diaphragm outer ring15 and the diaphragm inner ring 16.

[0089] In the case where the diaphragm outer ring insertion portion 12is fitted to the diaphragm outer ring 15, it is most preferable to setthe fitting dimension of the diaphragm outer ring insertion portion 12fitted to the diaphragm outer ring 15 to be in a range in which a gap of0.03 to 0.12 millimeters is formed along a surface of the head side ofthe diaphragm outer ring insertion portion 12 in the flow direction ofthe steam ST, and a gap of 0.03 to 0.12 millimeters is formed in asurface of the stepped block portion 18 on a diameter direction side (aside orthogonal to the flow direction of the steam ST) as shown in FIG.1.

[0090] On the other hand, in the case where the diaphragm inner ringinsertion portion 13 is fitted to the diaphragm inner ring 16, it ismost preferable to set the fitting dimension of the diaphragm inner ringinsertion portion 13 fitted to the diaphragm inner ring 16 to be in arange in which a gap of 0.03 to 0.12 millimeters is formed on thediameter direction side (side orthogonal to the flow direction of thesteam ST) of the columnar piece 20 of the diaphragm inner ring insertionportion 13 as shown in FIG. 1.

[0091] The setting of each of the fitting dimensions of the diaphragmouter ring insertion portion 12 fitted to the diaphragm outer ring 15and that of the diaphragm inner ring insertion portion 13 fitted to thediaphragm inner ring 16 to be in the range of 0.03 to 0.12 millimetersis based on the fact that if they are set to be 0.03 millimeters orless, the diaphragm outer and inner ring insertion portions 12 and 13cannot be assembled manually with the diaphragm outer and inner rings 15and 16 and that if they exceed 0.12 millimeters, plays are generated anda shakiness occurs to the assembled nozzle diaphragm during theoperation. An FEM (finite element method) analysis, a mock-up test orthe like also has confirmed that these fitting dimensions are the mostappropriate dimensions.

[0092] As is apparent from the above, according to this embodiment, thediaphragm outer ring insertion portion 12 is provided on one end of thenozzle blade (nozzle plate) 14, the diaphragm inner ring insertionportion 13 is provided on the other end thereof, the groove 23, to whichthe diaphragm outer ring insertion portion 12 is fitted, is provided inthe diaphragm outer ring 15, and the groove 28, to which the diaphragminner ring insertion portion 13 is fitted, is provided in the diaphragminner ring 16, whereby there can be provided the simple assembledstructure that does not require welding operation for welding thediaphragm outer ring insertion portion 12 and the diaphragm inner ringinsertion portion 13 to the respective grooves 23 and 28. Therefore,during the assembly of the turbine nozzle, a steam path 34 can be keptto have designed dimensions and the turbine nozzle can be operated withan improved turbine stage efficiency at low cost that does not accompanythe welding cost.

[0093] The assembling method of the nozzle diaphragm according to thepresent invention will be then described hereunder.

[0094]FIG. 21 is a schematic block diagram showing the steps of themethod of assembling the nozzle diaphragm according to the presentinvention.

[0095] The diaphragm outer ring 15 and the diaphragm inner ring 16,which are ring bodies when the nozzle diaphragm is completed, aremanufactured independently as the diaphragm outer ring upper halfportion 21 and the diaphragm outer ring lower half portion 22 obtainedby dividing the diaphragm outer ring 15 in half at a position ofsubstantially 180 degrees and as the diaphragm inner ring upper halfportion 26 and the diaphragm inner ring lower half portion 27 obtainedby dividing the diaphragm inner ring 16 in half at a position ofsubstantially 180 degrees, respectively. The grooves into which thenozzle blade 14 is fitted are preliminarily worked in the upper halfportions 21 and 26 and the lower half portions 22 and 27. That is, thecap-shaped groove 23 and the hook portion 24 are worked in the diaphragmouter ring upper half portion 21 and the diaphragm outer ring lower halfportion 22, respectively, whereas the concave groove 28 is worked in thediaphragm inner ring upper half portion 26 and the diaphragm inner ringlower half portion 27. Shapes of these grooves are set in advance sothat the diaphragm outer ring insertion portion 12 and the nozzle blade14 are surely engaged with the respective grooves.

[0096] Next, the nozzle blades 14 are sequentially inserted into theworked cap-shaped groove 23 and hook portion 24 from one side of thehorizontal joint surface HSJ1. The number of nozzle blades 14 to beinserted is determined in advance based on a pitch circle diameter (PCD)of this diaphragm and a pitch between the nozzle blades 14.

[0097] Among the inserted nozzle blades 14, the first and last insertednozzle blades 14, i.e., the two nozzle blades 14 facing the horizontaljoint surface HSJ1 of the diaphragm outer ring 15 are fixed relative tothe circumferential direction so that the nozzle blades 14 do not slipoff from the grooves of the outer rings by means of the stopper pieces31 a fixed to the diaphragm outer rings 15. Therefore, the insertednozzle blades 14 are fixed relative to the steam flow direction and anozzle blade longitudinal direction by engaging the hook portions 17 ofthe diaphragm outer ring insertion portions 12 provided on these nozzleblades 14 with the cap-shaped grooves 23 of the diaphragm outer rings 15and also engaging the block portions 18 of the diaphragm outer ringinsertion portions 12 provided on the nozzle blades 14 with the hookportions 24 of the diaphragm outer rings 15, respectively. Thus, it isnot particularly necessary to employ mechanical means such as bolts orpins or fixing means such as welding for fitting the diaphragm outerring insertion portions 12 of the nozzle blades 14 into the respectivediaphragm outer rings 15. On the other hand, in the circumferentialdirection, there is provided only means for preventing the nozzle blades14 from slipping off from the respective grooves by the stopper pieces31 a provided on the horizontal joint surface HSJ1, and the nozzleblades 14 are fixed to the grooves by contacting the adjacent bladeswith one another in the circumferential direction. The experiment andthe FEM analysis have confirmed that the gap of a portion, in which eachdiaphragm outer ring insertion portion 12 provided on the nozzle blade14 is fitted into the diaphragm outer ring 15, is optimally in the rangeof 0.03 to 0.12 millimeters in view of easiness of assembling,vibrations generated by the steam after assembly and the like.

[0098] In the next step, the diaphragm inner ring 16 is fitted into thediaphragm outer ring 15, to which each nozzle blade 14 is inserted, fromthe diaphragm inner ring insertion portion side of the nozzle blade 14.The fitting portion has a simple shape consisting of the concave groove28 provided in the diaphragm inner ring 16 and the convex columnar piece20 provided on the diaphragm inner ring insertion portion 13 of thenozzle blade 14. Because of this reason, it is unnecessary to take astep for sequentially inserting the nozzle blades 14 into the diaphragmouter rings 15 from the horizontal joint surface HJS1, but it sufficesto simply fit the diaphragm inner ring 16 into the diaphragm outer ring15 from the diaphragm inner ring insertion portion side of the nozzleblade 14. The experiment and the FEM analysis have confirmed that thegap of the portion, in which the diaphragm inner ring insertion portion13 provided on this nozzle blade 14 is fitted into each diaphragm innerring 16, is optimally set to be in the range of 0.03 to 0.12 millimetersin view of the assembling facilitation, the vibration generated by thesteam after the assembly and the like.

[0099] Next, each of the diaphragm inner ring 16 is fixed to the nozzleblade 14 by the stopper piece 31 b in a manner such that the stopperpiece 31 b fixes the nozzle blade 14 relative to the circumferentialdirection and fixes the diaphragm inner ring insertion portion 13 of thenozzle blade 14 to the diaphragm inner ring 16 to thereby prevents thediaphragm inner ring 16 from slipping off.

[0100] Finally, the diaphragm upper half portion (or diaphragm lowerhalf portion), in which the diaphragm outer ring 15, the nozzle blade 14and the diaphragm inner ring 16 are formed integrally, and the diaphragmlower half portion (or diaphragm upper half portion) formed similarlyare mated to each other on their horizontal joint surfaces, and then,the nozzle diaphragm is completed by screw-engaging a bolt with a bolthole provided in the diaphragm outer ring 15 of one of the diaphragmupper and lower half portions and a thread portion provided in the otherone of the diaphragm upper and lower half portion.

[0101] According to the assembling method of the characters mentionedabove, since the nozzle blade 14 is not fixed to the diaphragm innerring 16 and the diaphragm outer ring 15, even if any defect occurs tothe nozzle blade during the operation, only the nozzle blade to whichthe defect occurs can be exchanged without exchanging the entirediaphragm as in the conventional art.

[0102] Furthermore, since the fitting gap between the nozzle blade 14and the diaphragm inner ring 16 and that between the nozzle blade 14 andthe diaphragm outer ring 15 are set to be in the range of 0.03 to 0.12millimeters, no problem occurs to the nozzle blade insertion operationand the nozzle diaphragm can be operated without shakiness and with nomechanical fixing means even if a vibration is generated by the steamduring the turbine operation.

[0103]FIG. 11 is an elevational section representing the secondembodiment of the assembled nozzle diaphragm according to the presentinvention. In FIG. 11, like reference numerals are added to constituentelements corresponding to those in the first embodiment.

[0104] In the assembled nozzle diaphragm in this second embodiment, aT-shaped groove 35 is formed in the diaphragm outer ring 15, and thediaphragm outer ring insertion portion 12 fitted into this groove 35 isprovided with protruded hook portions 38 a and 38 b formed on anupstream side surface 36 directed toward the flow of the steam ST and ona downstream side 37 directed toward the flow of the steam ST,respectively, stepped block portions 39 a and 39 b continuous to therespective hook portions, and base portions 40 continuous to therespective block portions.

[0105] These continuous hook portions 38 a and 38 b, block portions 39 aand 39 b, and base portions 40 are all formed together with the nozzleblade 14 by precision forging or by being integrally cut out from anozzle blade element assembly by the machining work and formed so as toextend in the circumferential direction (moving blade rotating directionon the perpendicular plane relative to the steam flow). Since the otherconstituent elements are the same as those in the first embodiment, thedescriptions thereof are omitted herein.

[0106] As is apparent from the above, according to the this secondembodiment, the T-shaped cap groove 35 is formed in the diaphragm outerring 15, the upstream side surface 36 and the downstream side surface 37of the diaphragm outer ring insertion portion 12 are also formed by thecontinuous hook portions 38a and 38 b, the block portions 39 a and 39 band the base portions 40, respectively, and the hook portions 38 a and38 b and the block portions 39 a and 39 b of the diaphragm outer ringinsertion portion 12 are fitted into the groove 35 of the diaphragmouter ring 15, thus providing the simple assembled structure that doesnot require welding operation. Therefore, during the assembling of theturbine nozzle, a steam path 43 can be kept to have designed dimensionsand the turbine nozzle can be operated with highly improved turbinestage efficiency at low cost that does not accompany the welding cost.

[0107] In this embodiment, the so-called I-shaped diaphragm outer ringinsertion portion 12 having the protruded hook portions 38 a and 38 b,the stepped block portions 39 a and 39 b, and the protruded baseportions 40 formed on the upstream side surface 36 and the downstreamside surface 37, respectively, is fitted into the T-shaped cap groove 35formed in the diaphragm outer ring 15. However, the present invention isnot limited to this embodiment, and as shown in, for example, FIG. 12(the third embodiment), the diaphragm outer ring insertion portion 12formed by a columnar piece 42 and a protruded base portion 40 directedtoward a diameter direction (a direction orthogonal to the flow of thesteam ST) may be formed in a concave groove 41 formed in the diaphragmouter ring 15 and directed toward the diameter direction.

[0108] Further, the assembling steps of the nozzle diaphragm assemblingmethod in the second embodiment are substantially the same as those inthe first embodiment, so that the steps will not be described herein.

[0109]FIG. 13 is an elevational section representing the fourthembodiment of the assembled nozzle diaphragm according to the presentinvention. In FIG. 13, the same constituent elements as those in thesecond embodiment are denoted by the same reference numerals.

[0110] In the assembled nozzle diaphragm in this embodiment, a cap orcap-shaped groove 35 provided with a protruded hook portion 24 on aninlet side is formed in the diaphragm outer ring 15. The upstream sidesurface 36 of the diaphragm outer ring insertion portion 13 which isdirected toward the flow of the steam ST is also formed in combinationof the protruded hook portion 38 a, the stepped block portion 39 a andthe protruded base portion 40, and a ring piece 44 to be divided isattached to the block portion 39 a. A bolt 45 is also provided on thediaphragm outer ring 15 to apply a pressing force to the diaphragm outerring insertion portion 12, and a coupled surface on which the diaphragmouter ring insertion portion 12 m to be fitted to the groove 35, iscoupled to the diaphragm outer ring 15 is sealed. The other structuresare substantially the same as those of the first embodiment, so that thedetails thereof are now omitted herein.

[0111] Further, the continuous hook portion 38 a, block portion 39 a,and base portion 40 are all formed together with the nozzle blade 14 byprecision forging or by being integrally cut out from a nozzle bladeelement assembly by the machining work.

[0112] As is apparent from the above, in this fourth embodiment, at thetime when the diaphragm outer ring insertion portion 12 is fitted andinserted into the diaphragm outer ring 15, the ring piece 44 is theninterposed between the diaphragm outer ring insertion portion 12 and thediaphragm outer ring 15, and the coupled surface 46 between thediaphragm outer ring insertion portion 12 and the diaphragm outer ring15 is sealed due to the pressing force of the bolt 45 engaged with thediaphragm outer ring 15. Therefore, the shakiness of the turbine nozzlecan be surely prevented from causing and the turbine nozzle can be henceoperated stably.

[0113] Further, in this embodiment, by utilizing the pressing force ofthe bolt 45, the coupled surface between the diaphragm outer ringinsertion portion 12 and the diaphragm outer ring 15 is sealed.Therefore, it is not necessary to improve or maintain the accuracy ofthe fitting gap between the diaphragm outer ring insertion portion 12and the diaphragm outer ring 15, thus reducing the working cost.

[0114] Assembling steps of this nozzle diaphragm of the fourthembodiment will be described with reference to the schematic blockdiagram of FIG. 22. This nozzle diaphragm assembling method differs fromthat of the first embodiment in that at a time when the nozzle blade isinserted into the diaphragm outer ring, not only the nozzle blade butalso shakiness prevention pieces can be inserted into the diaphragmouter ring and in that the shakiness prevention pieces are fastened bythe bolt applied to the hook portion of the diaphragm outer ring tothereby fix or fasten the nozzle blades. Further, the steps other thanthe above steps are substantially the same as those in the firstembodiment shown in FIG. 21, so that they will not be described herein.

[0115]FIG. 14 is an elevational section illustrating the assemblednozzle diaphragm according to the fifth embodiment of the presentinvention. In FIG. 14, the same constituent elements as those in thesecond embodiment are denoted by the same reference numerals.

[0116] According to the assembled nozzle diaphragm in the fifthembodiment, the cap groove 35 provided with the protruded hook portionis formed in the inlet-side diaphragm outer ring 15, the upstream sidesurface 36 of the diaphragm outer ring insertion portion 12 fitted intothis groove 35, the surface 36 being directed toward the flow of thesteam ST, is formed in combination of the protruded hook portion 38 a,the stepped block portion 39 a.

[0117] A shakiness prevention piece 47 a is provided on a coupledsurface 46 a coupled with the diaphragm outer ring 15 on the head sideof the protruded hook portion 38 a to be parallel to the flow of thesteam ST, and a shakiness prevention piece 47 b is also provided on acoupled surface 46 b on the diameter direction side of the hook portion38 a of the upstream side surface of the diaphragm outer ring insertionportion 12. According to such arrangement, the shakiness preventionpiece 47 a prevents the shakiness of the diaphragm outer ring insertionportion 12 in the flow direction of the steam ST (direction of the steamturbine shaft), and on the other hand, the shakiness prevention piece 47b prevents the shakiness of the diaphragm outer ring insertion portion12 in the diameter direction (direction orthogonal to the flow of thesteam ST).

[0118] The other constituent elements are substantially the same asthose in the first embodiment, so that they will not be describedherein.

[0119] Further, the continuous hook portion 38 a, block portion 39 a,and base portion 40 are all formed together with the nozzle blade 14 byprecision forging or by being integrally cut out from a nozzle bladeelement assembly by the machining work.

[0120] As is apparent from the above, according to this embodiment, atthe time when the diaphragm outer ring insertion portion 12 is fittedand inserted into the diaphragm outer ring 15, the coupled surface 46 acoupled with the diaphragm outer ring 15 on the head side of theprotruded hook portion 38 a of the diaphragm outer ring insertionportion 12 parallel to the flow of the steam ST and the coupled surface46 b coupled with the diaphragm outer ring 15 on the diameter directionside of the hook portion 38 a are provided with the shakiness preventionpieces 47 a and 47 b, respectively. Therefore, it is ensured that theshakiness of the turbine nozzle can be prevented from causing and theturbine nozzle can be operated stably.

[0121] Further, in this embodiment, as mentioned above, since thecoupled surfaces 46 a and 46 b are provided with the shakinessprevention pieces 47 a and 47 b, respectively, it is not necessary toimprove the accuracy of the fitting gap between the diaphragm outer ringinsertion portion 12 and the diaphragm outer ring 15, thus reducing theworking cost.

[0122] Further, in this embodiment, in the diaphragm outer ringinsertion portion 12, the coupled surface 46 a coupled with thediaphragm outer ring 15. on the head side of the protruded hook portion38 a parallel to the flow of the steam ST and the coupled surface 46 bcoupled with the diaphragm outer ring 15 on the diameter direction sideof the hook portion 38 a are provided with the shakiness preventionpieces 47 a and 47 b, respectively. However, the present invention isnot limited to such arrangement of this embodiment, and as illustratedin FIG. 15, as sixth embodiment, for example, in the diaphragm outerring insertion portion 12, a shakiness prevention piece 47 c may befurther provided on a corner (shoulder) portion of the upstream sidesurface 36 on the head side of the protruded hook portion 38 a.Particularly, in the case where the shakiness prevention piece 47 c isprovided on the corner of the protruded hook portion 38 a, it ispossible to effectively prevent the shakiness of the diaphragm outerring insertion portion 12 in both the flow direction of the steam ST andthe direction orthogonal to the flow of the steam ST.

[0123]FIG. 16 is an elevational section illustrating the seventhembodiment of the assembled nozzle diaphragm according to the presentinvention. In FIG. 16, the same constituent elements as those in thesecond embodiment are denoted by the same reference numerals.

[0124] In the assembled nozzle diaphragm of this embodiment, thediaphragm outer ring insertion 12 provided on one end of the nozzleblade (nozzle plate) 14 and the diaphragm outer ring 15, to which thisdiaphragm outer ring insertion portion 12 is fitted, are constitutedsubstantially equally to those in the fourth embodiment shown in FIG.14. A nozzle blade inner periphery-side member 48 is provided,integrally with the nozzle blade 14, on the other end of the nozzleblade 14. That is, in this embodiment, the nozzle blade innerperiphery-side member 48 is formed integrally with the nozzle blade 14in place of the diaphragm inner ring insertion portion 13 and thediaphragm inner ring shown in FIG. 14. This embodiment is effective forthe case in which the distance between the nozzle blade 14 and theturbine shaft, not shown, is small.

[0125] Assembling steps of the nozzle diaphragm assembling method of thefifth to seventh embodiments are described through the schematic blockdiagram of FIG. 23. The nozzle diaphragm assembling method of this fifthto seventh embodiments differs from that in the first embodiment in thatwhen the nozzle blade is inserted into the diaphragm outer ring, notonly the nozzle blade but also the shakiness prevention pieces areinserted into the diaphragm outer ring. Further, the other steps aresubstantially the same as those of the first embodiment shown in FIG.21, so that they will not be described herein.

[0126]FIG. 17 is an elevational section illustrating the eighthembodiment of the assembled nozzle diaphragm according to the presentinvention. In FIG. 17, the same constituent elements as those in thefirst embodiment are denoted by the same reference numerals.

[0127] The assembled nozzle diaphragm in this embodiment is applied tothe steam turbine which operates to divide the flow of the steam to theleft flow and the right flow, such steam turbine being so-called acounter-flow (double flow) type. First and second divided-flow diaphragminner ring insertion portions 55 and 57 formed to bottoms of the firstand second divided-flow nozzle blades 49 and 50 for the steam ST areprovided with convex columnar pieces 57 and 58, respectively. Thecolumnar pieces 57 and 58 are fitted to a shared diaphragm inner ring 51shared between the first and second divided-flow nozzle blades 49 and50.

[0128] The first and second divided-flow diaphragm outer rings 52 and 53fitted into first and second divided-flow diaphragm outer ring insertionportions 55 and 56 of the first and second divided-flow nozzle blades 49and 50 are the same in configuration as the outer ring in the firstembodiment, so that they will not be described herein.

[0129] As can be seen from the above, according to this embodiment, thefirst and second divided-flow diaphragm inner ring insertion portions 55and 56 of the first and second divided-flow nozzle blade 49 and 50 arefitted into the shared diaphragm inner ring 51 shared between the firstand second divided-flow nozzle blades 49 and 50. It is, therefore,possible to further reduce the manufacturing cost and labor of theworker. When the assembled nozzle diaphragm is applied to the steamturbine, it is possible to continuously perform the stable operation fora long term without causing any problem of the distortion based on thewelding such as in the conventional art.

[0130] In this eighth embodiment, the example of applying the assemblednozzle diaphragm to the counterflow-type steam turbine has beendescribed. However, the present invention is not limited to thiscounterflow-type steam turbine, and as shown in, for example, FIG. 20,the assembled nozzle diaphragm of a fitting structure may be applied toso-called tie-in turbine stages constituted so that a first stagediaphragm outer ring 62, to which a first stage nozzle blade 59 and asecond stage nozzle blade 60 are fixed through welding portions 61 a, 61b, 61 c, and 61 d, is connected to a second stage nozzle diaphragm outerring 64 by means of bolt 66.

[0131] In this example, the assembled nozzle diaphragm may be appliedonly to the first stage nozzle diaphragm outer ring 62 and the secondstage nozzle diaphragm outer ring 64 or up to a first stage nozzlediaphragm inner ring 63 and a second stage nozzle diaphragm inner ring65.

[0132]FIG. 18 is an elevational section illustrating the ninthembodiment of the assembled nozzle diaphragm according to the presentinvention. In FIG. 18, the same constituent elements as those in thefirst embodiment are denoted by the same reference numerals.

[0133] In the assembled nozzle diaphragm in this embodiment,multiple-stage diaphragm outer ring insertion portions 69 such as afirst stage nozzle diaphragm outer ring insertion portion 67 of a firststage nozzle blade 59 and a second stage diaphragm outer ring insertionportion 68 of a second stage nozzle blade 60 are collectively fittedinto a multiple-stage diaphragm outer ring 70.

[0134] Further, the other constituent elements are substantially thesame to those in the first embodiment, so that they will not bedescribed herein.

[0135] As can be seen, in this embodiment, the multiple-stage diaphragmouter ring insertion portions 69 such as the first stage nozzlediaphragm outer ring insertion portion 67 of the first stage nozzleblade 59 and the second stage diaphragm outer ring insertion portion 68of the second stage nozzle blade 60 are collectively fitted to themultiple-stage diaphragm outer ring 70. Therefore, when the assemblingoperation is performed, the number of assembling steps and labor of theworkers can be further reduced.

[0136]FIG. 19 is an elevational section illustrating the tenthembodiment of the assembled nozzle diaphragm according to the presentinvention. In FIG. 19, the same constituent elements as those in thefirst embodiment are denoted by the same reference numerals.

[0137] In the assembled nozzle diaphragm in this embodiment, a plate 71of a fixed type, for example, is inserted into the diaphragm inner ring16 in the circumferential direction. Further, the other constituentelements are substantially the same as those in the first embodiment, sothat they will not be described herein.

[0138] As can be seen from the above, according to this embodiment, thestiffness of the assembled nozzle diaphragm can be intensified byinserting the fixed plate 71 into the diaphragm inner ring 16. It istherefore possible to effectively deal with cracks and the like based onan unexpected vibration resulting from an intermittent fluctuation inthe steam flow or a pressure fluctuation. This embodiment will beparticularly effective for the case that the diaphragm inner ring haslow stiffness.

INDUSTRIAL APPLICABILITY

[0139] As described hereinbefore, the assembled nozzle diaphragmutilizes the simple assembly structure in which the diaphragm outer ringinsertion portion provided on one end of the nozzle blade is fitted tothe diaphragm outer ring and in which the diaphragm inner ring insertionportion provided on the other end of the nozzle blade is fitted to thediaphragm inner ring. Therefore, in the case where the assembled nozzlediaphragm according to the present invention is applied to, for example,the steam turbine, the width of the steam path can be kept exactly atthe designed dimension, and the turbine nozzle can be operated with farhigher turbine stage efficiency.

[0140] In addition, according to the nozzle diaphragm assembling methodof the present invention, the nozzle blade can be freely moved relativeto the diaphragm inner and outer rings. Accordingly, even if a damagesuch as a crack occurs to the nozzle blade during the operation of thesteam turbine, it suffices to exchange only the nozzle blade to whichthe damage or the like occurs, and moreover, even in such case,differently from the conventional art, it is not necessary to exchangethe entire diaphragm and it is thereby possible to further reduceexchange operation. The present invention is thus be applicable toindustrial usage.

1. An assembled nozzle diaphragm comprising: a diaphragm outer ringhaving a groove opened toward an inner diameter side to be continuous inan inner peripheral direction of the diaphragm outer ring; a diaphragminner ring having a groove opened toward an outer diameter side to becontinuous in an outer peripheral direction of the diaphragm inner ring;and a nozzle blade having an insertion portion for the diaphragm outerring provided on one end and an insertion portion for the diaphragminner ring provided on the other end, wherein the groove opened towardthe inner diameter side of the diaphragm outer ring and the diaphragmouter ring insertion portion of the nozzle blade are shaped to be fittedto each other only in a circumferential direction of each of the grooveand the diaphragm outer ring insertion portion, and the groove openedtoward the outer diameter side of the diaphragm inner ring and thediaphragm inner ring insertion portion of the nozzle blade are shaped tobe fitted to each other only in one of circumferential direction anddiameter direction of each of the groove and the diaphragm inner ringinsertion portion.
 2. The assembled nozzle diaphragm according to claim1, wherein an upstream side surface of the diaphragm outer ringinsertion portion, which is directed toward a flow of a fluid, is formedin combination of a protruded hook portion and a stepped block portionprovided to be continuous to the protruded hook portion, and theprotruded hook portion and the stepped block portion extend in thecircumferential direction.
 3. The assembled nozzle diaphragm accordingto claim 1, wherein the diaphragm inner ring insertion portion has aconvex columnar piece formed at an intermediate position and the convexcolumnar piece extends in the circumferential direction.
 4. Theassembled nozzle diaphragm according to claim 1, wherein the diaphragmouter ring has a cap groove formed in the circumferential direction, thecap groove including a protruded hook portion at an inlet.
 5. Theassembled nozzle diaphragm according to claim 1, wherein the diaphragminner ring has a concave groove formed in the circumferential direction.6. The assembled nozzle diaphragm according to claim 1, wherein afitting gap between the diaphragm outer ring insertion portion and thediaphragm outer ring is set to be in a range of 0.03 to 0.12millimeters.
 7. The assembled nozzle diaphragm according to claim 6,wherein the fitting gap set to be in the range of 0.03 to 0.12millimeters between the diaphragm outer ring insertion portion and thediaphragm outer ring is at least one of a gap between a surface on ahead side of the diaphragm outer ring insertion portion parallel to aflow of a fluid and the diaphragm outer ring and a gap between a surfaceon an upstream side surface of the diaphragm outer ring insertionportion in the diameter direction and the diaphragm outer ring.
 8. Theassembled nozzle diaphragm according to claim 1, wherein a fitting gapbetween the diaphragm inner ring insertion portion and the diaphragminner ring is set to be in a range of 0.03 to 0.12 millimeters.
 9. Theassembled nozzle diaphragm according to claim 8, wherein the fitting gapset to be in the range of 0.03 to 0.12 millimeters between the diaphragminner ring insertion portion and the diaphragm inner ring is a gapbetween a surface of a columnar piece of the diaphragm inner ringinsertion portion in the diameter direction and the diaphragm innerring.
 10. The assembled nozzle diaphragm according to claim 1, whereinthe diaphragm outer ring insertion portion is formed in combination ofprotruded hook portions provided on an upstream side surface directedtoward a flow of a fluid and a downstream side surface along the flow ofthe fluid, respectively, stepped block portions provided to becontinuous to the respective protruded hook portions and protruded baseportions provided to be continuous to the respective stepped blockportions.
 11. The assembled nozzle diaphragm according to claim 1,wherein the diaphragm outer ring insertion portion is constituted incombination of a columnar piece directed toward the diameter directionand a protruded base portion provided to be continuous to the columnarpiece.
 12. The assembled nozzle diaphragm according to claim 1, whereinan upstream side surface of the diaphragm outer ring insertion portionwhich is directed toward a flow of a fluid is formed in combination of aprotruded hook portion, a stepped block portion provided to becontinuous to the hook portion, and a protruded base portion provided tobe continuous to the block portion, a ring piece is attached to theblock portion, and fixing means is provided on the diaphragm outer ringso as to apply a pressing force to the diaphragm outer ring insertionportion.
 13. The assembled nozzle diaphragm according to claim 1,wherein an upstream surface of the diaphragm outer ring insertionportion which is directed toward a flow of a fluid is formed incombination of a protruded hook portion, a stepped block portionprovided to be continuous to the hook portion, and a protruded baseportion provided to be continuous to the block portion, and a shakinessprevention piece is provided on a fitting surface on which the diaphragmouter ring insertion portion is fitted to the diaphragm outer ring. 14.The assembled nozzle diaphragm according to claim 13, wherein theshakiness prevention piece is provided at least one of a gap between asurface on a head side of the diaphragm outer ring insertion portionparallel to the flow of the fluid and the diaphragm outer ring and a gapbetween a surface of the upstream side surface of the diaphragm outerring insertion portion in the diameter direction and the diaphragm outerring.
 15. The assembled nozzle diaphragm according to claim 13, whereinthe shakiness prevention piece is provided in a corner of the upstreamside surface on a head side of the diaphragm outer ring insertionportion.
 16. The assembled nozzle diaphragm according to claim 1,wherein a plurality of the nozzle blades each supported by the diaphragmouter ring and the diaphragm inner ring are arranged at counterflowpositions along a flow of a fluid to be divided, and the plurality ofnozzle blades arranged at the counterflow positions are supported by thesingle diaphragm inner ring.
 17. The assembled nozzle diaphragmaccording to claim 1, wherein a plurality of the nozzle blades eachsupported by the diaphragm outer ring and the diaphragm inner ring arearranged at counterflow positions along a flow of a fluid to be divided,and the diaphragm outer ring insertion portion of each of the pluralityof nozzle blades arranged at the counterflow positions is supported bythe single diaphragm outer ring.
 18. An assembled nozzle diaphragmcomprising: a diaphragm outer ring having a groove opened toward aninner diameter side to be continuous in an inner peripheral direction ofthe diaphragm outer ring; a diaphragm inner ring having a groove openedtoward an outer diameter side to be continuous in an outer peripheraldirection of the diaphragm inner ring; and a nozzle blade having aninsertion portion for the diaphragm outer ring provided on one end andan insertion portion for the diaphragm inner ring provided on the otherend, wherein the diaphragm inner ring includes a nozzle blade innerperiphery-side member formed integrally with the nozzle blade.
 19. Theassembled nozzle diaphragm according to claim 18, wherein the diaphragmouter ring includes a shakiness prevention piece on a fitting surface onwhich the diaphragm outer ring insertion portion is fitted into thediaphragm outer ring.
 20. An assembled nozzle diaphragm comprising: adiaphragm outer ring having a groove opened toward an inner diameterside to be continuous in an inner peripheral direction of the diaphragmouter ring; and a nozzle blade having an insertion portion for thediaphragm outer ring provided on one end and a diaphragm inner ringprovided on the other end, wherein a plate is inserted into thediaphragm inner ring.
 21. A method of assembling a nozzle diaphragmwhich comprises: a diaphragm outer ring having a groove opened toward aninner diameter side to be continuous in an inner peripheral direction ofthe diaphragm outer ring; a diaphragm inner ring having a groove openedtoward an outer diameter side to be continuous in an outer peripheraldirection of the diaphragm inner ring; and a nozzle blade having aninsertion portion for the diaphragm outer ring provided on one end andan insertion portion for the diaphragm inner ring provided on the otherend, said method comprising the steps of: working the diaphragm outerring to be divided in half to a diaphragm outer ring upper half portionand a diaphragm outer ring lower half portion at a horizontal jointsurface position substantially at 180 degrees so as to constitute thediaphragm outer ring of a ring body; working the diaphragm inner ring tobe divided in half to a diaphragm inner ring upper half portion and adiaphragm inner ring lower half portion at a horizontal joint surfaceposition substantially at 180 degrees so as to constitute the diaphragminner ring of the ring body; fitting the diaphragm outer ring insertionportion of the nozzle blade from a horizontal joint surface of one ofthe diaphragm outer ring upper half portion and the diaphragm outer ringlower half portion toward a horizontal joint surface of the other one ofthe diaphragm outer ring upper half portion and the diaphragm outer ringlower half portion to sequentially insert, one by one, the nozzle bladesof a preset number in a circumferential direction; fixing the pluralityof inserted nozzle blades by stopper pieces on the horizontal jointsurfaces of the one half portion and on the horizontal joint surface ofthe other half portion, respectively; inserting the diaphragm inner ringupper half portion and the diaphragm inner ring lower half portion intothe inner ring insertion portion of the nozzle blade from an insidediameter direction of the inner ring insertion portion; fixing theplurality of inserted nozzle blades by stopper pieces on the horizontaljoint surface of the inserted diaphragm inner ring upper half portionand the horizontal joint surface of the inserted diaphragm inner ringlower half portion, respectively; and fixing the diaphragm inner ringupper half portion and the diaphragm outer ring upper half portionintegrated with the nozzle blades of the preset number to the diaphragminner ring lower half portion and the diaphragm outer ring lower halfportion integrated with the nozzle blades of the preset number on therespective horizontal joint surfaces.
 22. The nozzle diaphragmassembling method according to claim 21, wherein a fitting gap betweenthe diaphragm outer ring insertion portion and the diaphragm outer ringis set to be in a range of 0.03 to 0.12 millimeters.
 23. The nozzlediaphragm assembling method according to claim 22, wherein the fittinggap set to be in the range of 0.03 to 0.12 millimeters between thediaphragm outer ring insertion portion and the diaphragm outer ring isat least one of a gap between a surface on a head side of the diaphragmouter ring insertion portion parallel to a flow of a fluid and thediaphragm outer ring and a gap between a surface on an upstream sidesurface of the diaphragm outer ring insertion portion in the diameterdirection and the diaphragm outer ring.
 24. The nozzle diaphragmassembling method according to claim 21, wherein a fitting gap betweenthe diaphragm inner ring insertion portion and the diaphragm inner ringis set to be in a range of 0.03 to 0.12 millimeters.
 25. The nozzlediaphragm assembling method according to claim 24, wherein the fittinggap set to be in the range of 0.03 to 0.12 millimeters between thediaphragm inner ring insertion portion and the diaphragm inner ring isin the diameter direction of a columnar piece of the diaphragm innerring insertion portion.